TwinsDiseases in TwinsPregnancyTwins, MonozygoticTwins, ConjoinedTwins, DizygoticPregnancy OutcomePregnancy ComplicationsPregnancy, AnimalGestational AgePregnancy, TwinPregnancy Trimester, FirstPregnancy, MultiplePregnancy, EctopicPregnancy Trimester, ThirdTwin Studies as TopicPregnancy Trimester, SecondPregnancy Complications, CardiovascularPregnancy RatePregnancy TrimestersPregnancy TestsUltrasonography, PrenatalInfant, NewbornFetusPregnancy in DiabeticsPlacentaPregnancy, TubalFetal DeathPregnancy Complications, NeoplasticPregnancy Complications, InfectiousAbortion, SpontaneousPregnancy in AdolescencePregnancy, High-RiskBirth WeightPregnancy ProteinsMaternal-Fetal ExchangeUterusPre-EclampsiaFetal DevelopmentPrenatal Exposure Delayed EffectsPregnancy, UnplannedFetal DiseasesPregnancy, ProlongedPregnancy, UnwantedFetal Growth RetardationPremature BirthPregnancy Complications, HematologicLactationParityAbortion, InducedObstetric Labor, PrematureEmbryo TransferTripletsCesarean SectionFertilization in VitroEmbryo ImplantationAmniotic FluidLabor, ObstetricPrenatal CareEmbryonic and Fetal DevelopmentPregnancy Reduction, MultifetalPregnancy, AbdominalPrenatal DiagnosisFetal WeightPregnancy MaintenanceFetofetal TransfusionInfant, PrematurePregnancy Complications, ParasiticCongenital AbnormalitiesDelivery, ObstetricLitter SizeMaternal ExposureMaternal Nutritional Physiological PhenomenaHypertension, Pregnancy-InducedProspective StudiesChorionTrophoblastsAbnormalities, Drug-InducedFetal HeartCrown-Rump LengthPlacental CirculationMaternal AgeRisk FactorsPlacenta DiseasesInfant, Low Birth WeightPrenatal Nutritional Physiological PhenomenaAbortion, TherapeuticDeciduaStillbirthParturitionCohort StudiesDiabetes, GestationalReproductive Techniques, AssistedPlacentationFetal BloodInfant, Small for Gestational AgeInfertility, FemaleAmniocentesisAbortifacient Agents, NonsteroidalFertility